No matter how good a time you’re having in bed, certain things are guaranteed to kill the mood. Examples: your parents walking in on you when your ass is pointing skyward or someone having a deeply uncool reaction to perfectly normal bodily functions. But breaking someone’s penis belongs in a whole other league of sexual buzzkills.

Before understanding how dick damage occurs, you have to know what a penis is—and is not—made of.

OK, so technically, you can’t break a penis, because they lack one very important qualification. “People call them boners, but there’s no bone in the penis,” Mark Hong, M.D., a urologist in Phoenix, Arizona, tells SELF. When it comes to medical terminology, what we’re talking about here is penile fractures.

“The penis is basically a spongy tube of blood vessels, or corpora cavernosa, wrapped in a very durable, almost rubbery layer,” Paul R. Shin, M.D., a urologist at Shady Grove Fertility in the Washington, D.C. area, tells SELF. That layer is called the tunica albuginea, or the membrane of the penis that allows the spongy tissue to swell with blood when someone gets erect, says Hong.

Penile fractures happen when that membrane cracks or ruptures in some way. “There will be an immediate loss of erection, you’ll hear a popping noise, and there will be a lot of bruising and swelling,” says Shin. Basically, there won’t be any question that something is really, really wrong.

Unfortunately, sex is prime time for penile fractures to occur.

The most common scenario is a “mistimed thrust” in a woman-on-top situation, after the penis has slipped out of the vagina, says Shin. (A 2014 study in Advances in Urology backs this up.) If you push down with all your might when the penis isn’t perfectly lined up with your vagina, it can be too much for one body part to handle.

Lest you think that avoiding anything cowgirl-related will put you in the clear, Shin says, “I’ve seen [penile fractures] happen from every other position as well.” Great!

The mechanics are basically the same, just flipped into a different pose. “Immediately around the vagina, there’s the pubic bone,” says Hong. “If someone’s penis slips out and ends up banging into the bone, you have one hard structure meeting another. Sometimes the pubic bone wins out.”

So, yes, it can happen in any sex position, but it’s not likely enough that you need to worry about it every time you have sex, says Shin.

If you’re ever unlucky enough to inflict this kind of injury, there’s only one thing to do.

Getting medical attention for the person you’re with should be your top priority. You can ice your partner’s penis a bit before you leave, but what’s most important is finding a doctor ASAP. “I’ve seen guys try to wait this out, and the biggest reason is because it’s embarrassing to walk into the ER or a doctor’s office with broken penis,” says Hong. “But it’s an emergency.”

Since the penis’ membrane is such a key part of getting and maintaining an erection, if a penile fracture isn’t fixed immediately, a man can eventually have issues with erectile dysfunction, says Shin. Even when treated promptly, some penises form scar tissue after healing. If that scar tissue becomes severe enough, it can cause what’s known as Peyronie’s disease, or an extremely curved penis that makes it hard to have sex, says Shin. That’s rare, though, and it’s really the only way this kind of injury can affect a man’s fertility, he explains.

Most people who experience a penile fracture make a full recovery. “If it’s addressed appropriately and repaired in a timely manner, most men don’t have problems with long-term functionality,” says Shin. If you ever find yourself with a penile fracture on your hands (or between your legs), remember that very important fact—then locate the nearest ER.